The present invention relates to power amplifier systems. It finds particular application in conjunction with dynamic power amplifier systems, and will be described with particular reference thereto. It will be appreciated, however, that the invention is also amenable to other like applications.
When radio power is to be radiated (or received) by electronically scanning one (1) or more beams over a wide angular range with optimum efficiency, it is possible to use either passive or active antennas. Passive antennas include a main amplifier followed by a fixed or variable power divider together with phase shifters and/or switches. Active antennas incorporate radio-frequency amplifiers.
In conventional systems, antennas are positioned to radiate in corresponding directions. For example, three (3) antennas may be positioned to broadcast in three (3) respective sectors of a 360 degree angular range (i.e., each sector includes 120 degrees). Respective sets of amplifiers are electrically connected to the antennas in each of the sectors. Each set of amplifiers increases the power of the respective source signals before the signals are transmitted from the antennas. The maximum amount of power incorporated into any one of the source signals is a function of the number of amplifiers in each of the respective sets.
As discussed above, each of the amplifiers in conventional systems only communicates with a specific antenna and cannot be selectively switched to another one of the antennas in the system. Therefore, the power provided by the amplifiers cannot be selectively allocated among the antennas.
Assuming each antenna in the system only communicates with one set of amplifiers, the power output from any one antenna is a function of the number of amplifiers in the set. In other words, it is not possible for an antenna to communicate with an amplifier in another set of amplifiers. Therefore, if one of the amplifiers fails, the power output of the antenna connected to the failed amplifier decreases accordingly.
One method of compensating for failed amplifier(s) is redundancy. Redundancy involves incorporating additional amplifier(s) into each set of amplifiers communicating with an antenna. The additional amplifier(s) are not used unless one (1) or more of the amplifiers within the set fails. More specifically, the additional amplifiers are kept in an "off" state unless one (1) or more of the primary amplifiers fails. In this sense, the additional amplifier(s) act as backups to the primary amplifiers. Therefore, if one (1) of the primary amplifiers within a set fails, the additional amplifier(s) are switched on in order to compensate for the failure.
While redundancy provides backup amplifiers in the event that one (1) or more amplifier fails, conventional implementations of redundancy also increase the total cost and weight of the antenna system. More specifically, redundancy typically increases the total number of amplifiers in the antenna system. The increased cost and weight are undesirable. A need exists to provide redundancy without increasing the total number of amplifiers in an antenna system.
The present invention provides a new and improved apparatus and method which overcomes the above-referenced problems and others.